How to upgrade from Windows 8.0 to 8.1 while keeping all the apps?

Solution 1:

Upgrading to Windows 8.1 from windows 8 without losing apps is possible. There are two things to note here 1) The installation language must match your system's default UI language and 2) a specific Windows 8 edition can only be upgraded to its equivalent or higher edition.

For example, if you have Windows 8 Pro English-GB installed, then you can only upgrade to Windows 8.1 Pro English-GB or Windows 8.1 Enterprise English-GB without compromising application data.

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